Conventionally, a motor control circuit for an electric power tool included a duty ratio control circuit for controlling an output power device which is interposed in a path for supplying electric current to an electric motor to control the torque output of the motor. A variable resistor is included in the control circuit, and the operator can control the rotational speed and the torque output of the motor in a continually variable fashion by adjusting the variable resistor as required.
Such a control circuit offers a high level of convenience to the user, but the need for a variable resistor and a complex control circuit means a high manufacturing cost, and ensuring necessary levels of reliability and durability presents an added difficulty.
To eliminate this problem, it is possible to control the output of the motor in two steps, and reduce the manufacturing cost through the use of a two-position switch mechanism instead of using a variable resistor. However, as the motor can be controlled only in two steps, a satisfactory level of convenience cannot be obtained.